The present invention relates to a reflecting mirror unit for use with a laser beam machine to set up the optical path of a laser beam.
FIG. 6 is a cross-sectional view showing a bend mirror device that is the conventional reflecting mirror unit as disclosed in JP-A-63-164701, for example. In FIG. 6, reference numeral 1 denotes a mirror, and reference numeral 3 denotes a mirror container for containing the mirror 1, in which the mirror 1 is fixed within this mirror container 3 by a pressing member 7. The pressing member 7 is provided with an air inlet opening 13 and an air outlet opening 15 to cool the mirror 1 through the air. Also, reference numeral 5 denotes a spherical body, reference numeral 9 denotes a screw for securing this spherical body 5 in the mirror container 3, reference numeral 17 denotes a carrier for carrying an outer circumferential face of the spherical body 5 around its inner spherical surface, reference numeral 25 denotes a cap that is secured to the carrier 17 by a screw 23, reference numeral 27 denotes an adjusting bolt attached on the cap 25, and reference numeral 35 denotes a block for securing the carrier 17.
The operation will be now set forth. An incident light Li is reflected at a point P on a reflection surface of the mirror 1, and becomes an emergent light Lo. The alignment of optical axis for this emergent light Lo, or the adjustment of angle of reflection for the mirror 1, is made by the adjusting bolt 27 that presses a back face of the mirror container 3 to force the spherical body 5 to change the angle of reflection while sliding with the carrier 17.
The conventional reflecting mirror unit is constituted as described above, and had a problem that after adjusting the angle (direction of the reflection surface) of the mirror 1 by the adjusting bolt 27, the angle of the mirror 1 was drifted due to the vibration and changes in the temperature, because there is no means for securing the mirror 1. For this measure, the maintenance such as a periodical inspection must be practiced, and required some skills to make the adjustments. Moreover, this amount of drift, including less uniform change with the time, resulted in poor reliability in the management of precision.
There was another problem that when the angle of the mirror 1 is fixed by applying more torque to the adjusting bolt 27 after adjustment, the fixing force is not applied uniformly, causing a moment to drift the angle of the mirror 1. Also, there was another problem that the residual stress caused by the fixing force is released with the elapse of the time, drifting the angle gradually.
An angle adjusting mechanism for the adjusting bolt 27 is not employed once the adjustment for the angle of the mirror 1 is finished, except for rare cases including a failure of the reflecting mirror unit or an exchange of the parts. However, since the angle adjusting mechanism is always integrated with the reflecting mirror unit main body in a normal state, namely, while the laser beam machine is being used, the back face portion of the mirror 1 is increased, and the reflecting mirror unit is thickened as a whole as indicated by size t in FIG. 6.
As described above, the angle adjusting mechanism that is not usually employed is integrated with the reflecting mirror unit, whereby there was another problem that it is difficult to reduce the reflecting mirror unit in weight and size, and it is likely to interfere with other components.
In the conventional example, though a concave portion that is formed inside the carrier 17 sliding with the outer circumferential face of the spherical body 5 is a spherical surface, it is practically required to have some interstice between both spherical surfaces (i.e., a convex spherical surface and a concave spherical surface) of the spherical body 5 and the carrier 17 to allow the operation of inserting the spherical body 5 and adjusting the angle of the mirror 1. Therefore, it is necessary that the concave shape (i.e., concave spherical surface) inside the carrier 17 is formed to have a slightly greater radius of curvature than the spherical shape (convex spherical surface) of the outer circumferential face of the spherical body 5. When both the faces of the carrier 17 and the spherical body 5 are worked as the spherical surfaces (i.e., concave spherical surface and convex spherical surface), they are not easily finished at a desired precision. Hence, in practice, the spherical surface of the spherical body 5 and the concave spherical surface of the carrier 17 are not contact over a certain area, and a part of the spherical surface of the spherical body 5 inscribed by the concave spherical surface of the carrier 17 is mostly an end portion of a circular arc of the concave spherical surface inside the carrier 17, or an edge portion 18. The edge portion 18 is usually deformed due to working distortion, and is so thin as to be prone to the elastic deformation and plastic deformation owing to a stress. Hence, there was a further problem that, when the spherical body 5 is pressed onto the edge portion 18 to cause a stress concentration, the edge portion 18 that is a contact portion is easily deformed, giving rise to a drift in the angle of the mirror 1.
This invention has been achieved to solve the above-mentioned problems, and it is an object of the invention to provide a reflecting mirror unit which can be retained firmly in a fixed state after adjusting the angle of a mirror, and that can be reduced in size (thickness) and weight.
The present invention provides a reflecting mirror unit comprising a mirror, mirror holding means for holding the periphery of the mirror, in which an outer circumferential portion perpendicular to a reflection surface of the mirror is shaped like a circular arc in cross section, a first carrier that is contact with a part of the outer circumferential portion on the mirror reflection surface side for the mirror holding means at a part of its inner conical surface, a second carrier that is opposed via the mirror holding means to the first carrier, and is contact with a part of the outer circumferential portion on the mirror back face side for the mirror holding means at a part of the inner conical surface, and pressure securing means for pressing the first carrier and the second carrier against the mirror holding means.
Accordingly, the surface of the mirror holding means and the surface of the first carrier have a straight line and a circular arc contacted, respectively, as seen in cross section, but the contact between the straight line and the circular arc is more beneficial in view of the practical working precision than the contact between the circular arcs, and a contact portion between the mirror holding means and the first carrier is less likely to be deformed. Consequently, the adjustment for the angle of mirror can be made at higher precision, and the mirror is held and fixed securely, so that the drift in the angle of the mirror can be reduced greatly.
Also, this invention provides a reflecting mirror unit that consists of a unit main portion having a mirror, mirror holding means for holding the periphery of the mirror, in which an outer circumferential portion perpendicular to a reflection surface of the mirror is shaped like a circular arc in cross section, a first carrier that is contact with a part of the outer circumferential portion on the mirror reflection surface side for the mirror holding means at a part of its inner conical surface, a second carrier that is opposed via the mirror holding means to the first carrier and is contact with a part of the outer circumferential portion on the mirror back face side for the mirror holding means at a part of the inner conical surface, and pressure securing means for pressing the first carrier and the second carrier against the mirror holding means, and mirror adjusting means, which is provided to be separable from the unit main portion, for adjusting a reflection direction of the mirror in a state where the mirror holding means and the first carrier are contacted.
Accordingly, the mirror adjusting means is separable from the unit main portion having a main portion of the reflecting mirror unit including the second carrier, so that the reflecting mirror unit can be reduced in size, and inparticular in thickness and weight.
Also, this invention provide a reflecting mirror unit with an elastic member having a finite width in an inner circumferential direction in a range of the inner conical surface of the second carrier including a contact area with the mirror holding means.
Accordingly, the mirror can be fixed more precisely to prevent the drift in the angle of the mirror (reflection direction) in the fixing operation.